One of high-capacity storage batteries for storing electricity of new energy from solar photovoltaic power generation and wind power generation is a flow battery, typically a redox flow battery (RF battery). The RF battery is charged or discharged using the oxidation-reduction potential difference between ions contained in a positive electrolyte and ions contained in a negative electrolyte (refer to, for example, Patent Literature 1). As illustrated in FIG. 9 of the principle of the operation of a RF battery α, the RF battery α includes a battery cell 100 divided into a positive electrode cell 102 and a negative electrode cell 103 by a proton-permeable membrane 101. The positive electrode cell 102 contains a positive electrode 104, and is connected via ducts 108 and 110 to a positive electrolyte tank 106, which stores a positive electrolyte. The duct 108 is equipped with a pump 112. These members 106, 108, 110, and 112 constitute a positive circulation line 100P, which circulates the positive electrolyte. Similarly, the negative electrode cell 103 contains a negative electrode 105, and is connected via ducts 109 and 111 to a negative electrolyte tank 107, which stores a negative electrolyte. The duct 109 is equipped with a pump 113. These members 107, 109, 111, and 113 constitute a negative circulation line 100N, which circulates the negative electrolyte. The electrolytes stored in the tanks 106 and 107 are circulated by the pumps 112 and 113 through the cells 102 and 103 during charge and discharge. When charge or discharge is not performed, the pumps 112 and 113 are stopped and the electrolytes are not circulated.
In general, the battery cell 100 is formed within a structure referred to as a battery cell stack 200 in FIG. 10. The battery cell stack 200 is constituted by sandwiching, from both sides, a multilayer structure referred to as a substack 200s with two end plates 210 and 220, and fastening the substack 200s with a fastening mechanism 230 (FIG. 10 illustrates a configuration using plural substacks 200s). As illustrated in the upper part of FIG. 10, the substack 200s has a configuration in which cell units constituted by a cell frame 120, a positive electrode 104, a membrane 101, a negative electrode 105, and a cell frame 120 are stacked, and the stack body is sandwiched between supply/drainage plates 190 and 190 (refer to the lower part of FIG. 10). Such a cell frame 120 in the cell unit includes a frame 122 including a through-window and a bipolar plate 121 blocking the through-window. The positive electrode 104 is disposed on and in contact with one surface side of the bipolar plate 121. The negative electrode 105 is disposed on and in contact with the other surface side of the bipolar plate 121. In this configuration, a single battery cell 100 is formed between bipolar plates 121 of adjacent cell frames 120.
In the substack 200s, supply and drainage of electrolytes through the supply/drainage plates 190 and 190 to and from the battery cells 100 are performed with liquid supply manifolds 123 and 124 and liquid drainage manifolds 125 and 126, which are formed in the frames 122. The positive electrolyte is supplied from the liquid supply manifold 123 through an inlet slit formed in one surface side (exposed side in the drawing) of the frame 122 to the positive electrode 104, and drained through an outlet slit formed in an upper portion of the frame 122 to the liquid drainage manifold 125. Similarly, the negative electrolyte is supplied from the liquid supply manifold 124 through an inlet slit (represented by dotted lines) formed in the other surface side (hidden side in the drawing) of the frame 122 to the negative electrode 105, and drained through an outlet slit (represented by dotted lines) formed in an upper portion of the frame 122 to the liquid drainage manifold 126. Ring-shaped sealing members 127 such as O-rings or flat gaskets are disposed between the cell frames 120 to suppress leakage of electrolytes from the substack 200s. 
Input and output of electric power between the external apparatus and the battery cells 100 in the substacks 200s are performed with a current-collecting structure using current collector plates formed of a conductive material. A pair of current collector plates is disposed for each of the substacks 200s; and the current collector plates are individually electrically connected to, among plural cell frames 120 stacked, the bipolar plates 121 of cell frames 120 that are disposed at both ends in the stack direction.